How long can a louse survive without blood? - briefly
A head louse typically survives only one to two days without a blood meal; body lice can endure up to about a week under optimal conditions.
How long can a louse survive without blood? - in detail
A louse requires a regular blood meal to maintain metabolic processes. When deprived of host blood, survival varies with species, developmental stage, temperature, and humidity.
Adult head‑lice (Pediculus humanus capitis) typically die after 24–48 hours without feeding. Laboratory observations show that at 30 °C and 70 % relative humidity, mortality reaches 100 % within two days. Lower temperatures extend survival modestly; at 10 °C, adults may persist for up to five days, but physiological activity is minimal.
Adult body‑lice (Pediculus humanus humanus) survive longer off the host. Under ambient indoor conditions (20–25 °C, 50–60 % humidity), they can remain viable for 7–10 days. The extended lifespan reflects a thicker exoskeleton and reduced metabolic rate compared to head‑lice.
Nymphal stages are less tolerant. First‑instar nymphs die within 12–24 hours without blood, while later instars survive 24–36 hours under optimal humidity. Their smaller energy reserves limit endurance.
Eggs (nits) are not dependent on blood. They remain viable for several weeks, hatching only when environmental conditions permit a subsequent blood meal for the emerging nymph.
Key factors influencing starvation tolerance:
- Temperature: higher temperatures increase metabolic demand, shortening survival; cooler environments slow metabolism.
- Relative humidity: low humidity accelerates desiccation, reducing lifespan; moderate humidity (60–80 %) prolongs viability.
- Species: body‑lice exhibit greater off‑host endurance than head‑lice due to physiological differences.
- Developmental stage: adults outlast nymphs; eggs are independent of blood supply.
In summary, adult head‑lice survive roughly one to two days without a blood source, adult body‑lice up to a week or more, nymphs less than two days, and eggs persist for weeks until conditions allow hatching.